The new program, which the City Council approved last week, targets 1,800 especially flood-prone buildings and offers owners a rebate of up to $2,500 to install a backwater valve, which prevents over-capacity sewers from flooding into basements.

An initial letter will go out in early September to those 1,800 properties, introducing residents to the rebate program, city spokeswoman Meghan Pembroke said.

Follow-up letters will include more detail, including the six-month deadline that residents will need to adhere to in order to qualify for the rebate.

Maintaining the valve will be the owner’s responsibility. The rebate will also be applicable to disconnecting a downspout from the sewer in homes where that is appropriate.

If the owner declines to participate in the rebate program, the city will eventually install a backwater valve in the public right-of-way, but that might not happen for up to three years, the amount of time the city estimates it will take to install valves on all 1,800 properties.

The second part of the program limits the city’s liability for flooding, capping claims at $25,000 per building or $5,000 per unit in the case of rental property.

While property owners aren’t required to disconnect their downspouts, assistant city attorney Tim Benedict emphasized to the council that the city won’t settle any claims from those owners if their properties flood.

The backwater valve installation program is intended to address the immediate need of stopping flooding during major storms.

The city has also been installing the valves as part of settlements with property owners left over from last year’s storms.

The city is also developing a more long-term sewer plan which may involve a partial or full separation of the city’s stormwater and sewage pipes. The combined system covers 1.1 square miles of northern Everett and has 145 miles of pipe.

Separating the entire combined system would cost up to $1 billion, raise sewer rates to about $250 per month and take three decades to complete.

The city is likely to develop a more limited plan. But even the smallest separation project under consideration has an stimated price tag of $283 million, would take 10 years to complete, and still cause sewer rates to double to about $100 per month.